The present invention relates to photogrammetric block adjustments and more particularly to mapping image coordinates from a photographic picture or image to ground coordinates using a Rational Polynomial Camera block adjustment.
Topographical maps, orthophoto maps, Digital Elevation Models, and many other metric products are generated from satellite and aerial images. In order to satisfy accuracy requirements for these metric products, a need exists for an accurate mathematical sensor model relating an image coordinate space to an object coordinate space. As shown in FIG. 1, an image coordinate space 110 is a 2-dimensional coordinate system defined only with respect to the image. An object coordinate space 120, however, is a 3-dimensional coordinate system defined with respect to an object being imaged (the imaged object is not shown in FIG. 1) on the ground 130. As will be explained further below, mathematical sensor models allow one to determine the object coordinates in object coordinate space 120 of the object being imaged from the image coordinates in image coordinate space 110. However, these mathematical sensor models are complex. Therefore, it would be desirous to develop a simplified model.
The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings. It is an object of the present invention to describe a simplified method and apparatuses for photogrammetric block adjustment. The present invention uses simple offsets, scale factors, and polynomial adjustment terms in either image or object space to achieve effects analogous within a high degree of accuracy to the effects achieved by adjustment of physical model parameters.
It is a further object of the present invention to have a method of photogrammetric block adjustment that does not present the numerical ill-conditioning problems of classical techniques. The numerical conditioning is achieved by having only one adjustment parameter that represents multiple physical processes that have substantially the same effect.
Another object of the present invention is to simplify development of photogrammetric block adjustment software by utilizing a generic camera model describing object-to-image space relationships and a generic adjustment model for block-adjusting parameters of that relationship. Use of generic models reduces the effort associated with developing individual camera models.
Described is an algorithm for photogrammetric block adjustment of satellite images. The object-to-image relationship of each image in the block of images is described by a rational polynomial camera (RPC) mathematical model. To the basic object-image model of each image, an adjustment model is added. The adjustment model comprises simple offsets, scale-factors, and/or polynomial adjustment terms in either object or image space.